Hordes of yabbies are trashing rivers in Africa. How did this happen?
In the 1980s and 1990s, the hardy redclaw crayfish was exported from Australia around the world. But escapee yabbies have become a nightmare.
Every year, the upper Zambezi River overflows its banks, flooding vast floodplains in Zambia. These wetlands are home to exceptional biodiversity, including unique species of birds and fish. However, recent signs indicate significant disturbances in the ecosystem. Native fish and invertebrate populations have declined, river vegetation is being consumed, and river banks are deteriorating.
This phenomenon is attributed to the presence of redclaw crayfish (Cherax quadricarinatus), a freshwater crustacean native to Australia and Papua New Guinea.
Redclaw crayfish thrive in harsh, dry conditions, making them well-adapted to the seasonal floodplains of the Zambesi River. They reproduce rapidly, laying up to 1,000 eggs per brood, and can survive in oxygen-depleted environments by burrowing and entering a dormant state for extended periods. Their hardiness, coupled with their aggressive feeding habits, allows them to outcompete native species for resources.
Redclaw crayfish were introduced to Africa in the 1980s and 1990s for aquaculture, aquarium trade, and as pets. Once released into the wild, they multiplied quickly and began causing ecological damage. In Zambia, their numbers have surged, leading to declines in native plant, fish, and invertebrate populations. Their rapid spread – up to 49 kilometers per year during flooding seasons – threatens to spread to sensitive ecosystems like the Okavango Delta and Kruger National Park.
While redclaw crayfish are not the only invasive species causing trouble, they are particularly resilient due to their evolutionary history in Australia's extreme climate. As climate change brings more extreme weather, species like the redclaw are better equipped to survive, posing a threat to globally sensitive water systems. Efforts to eradicate these invasive species are largely futile once established, highlighting the challenges of managing invasive species in new environments.
Written by urgent.news from The Conversation AU's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
